The present invention relates to improvements in apparatus for transporting discrete commodities, particularly for intermittently transporting several files of stacks consisting of paper sheets or the like. More particularly, the invention relates to improvements in apparatus for intermittent transport of two or more files of spaced-apart stacks or piles of superimposed sheets or the like. Still more particularly, the invention relates to improvements in apparatus of the type wherein each file of stacks is transported by at least three endless conveyors in the form of belts or chains which are disposed in parallel vertical planes and are provided with entraining elements in the form of projections or lobes serving to advance as well as to locate the stacks during transport along a predetermined path.
The aforementioned commonly owned copending application Ser. No. 343,742 discloses a transporting apparatus wherein three transporting units are disposed side by side, and each such unit comprises three belts including a centrally located belt whose projections engage the front edge faces of the stacks and two outer belts whose projections engage the rear edge faces of the stacks on or above the respective transporting unit. The belts are trained around pairs of pulleys, and the drive means for the belts comprises a first shaft which transmits torque to the pulleys for the outer belts in each transporting unit and a second shaft which transmits torque to the pulleys for the centrally located belt in each unit. The two shafts receive motion from a common stepping motor.
The apparatus of the aforementioned commonly owned copending application Ser. No. 343,742 operates quite satisfactorily once a stack of paper sheets is properly located between a (leading) projection of the centrally located belt and the (trailing) projections of the outer belts forming part of a transporting unit. However, problems can arise in connection with the delivery of stacks onto the transporting units because the distance between the projections of the centrally located belt and the projections of the outer belts in each transporting unit is fixed. Therefore, it is necessary to urge the leading edge face of a freshly delivered stack against a projection of the centrally located belt while the corresponding projections of the outer belts advance from a lower level to a higher level in order to engage the trailing edge face of such freshly delivered stack. Similar problems can be encountered during removal of stacks from the path which is defined by the transporting apparatus, e.g., from the upper surface of a platform which is installed at a level above the upper reaches of the belts in each of the transporting units. As a rule, it is necessary to accelerate the stacks once the leading projections (on the respective centrally located belts) descend below the associated platforms in order to make sure that the corresponding trailing projections will have room to descend to a level below the platform during movement around the pulleys at the downstream ends of the respective transporting units. If the aforedescribed precautionary measures are not fulfilled, e.g., if the leading edge face of a stack is not urged against the projection of the centrally located belt in the respective transporting unit, the oncoming projections of the outer belts are likely to lift the rear portion of the stack with attendant shifting of sheets in the stack relative to one another. Furthermore, the rising trailing projections which are to engage the trailing edge face of a freshly delivered stack are likely to score or to otherwise deface the sheets of the stack. The trailing projections are also likely to shift the sheets of a stack at the discharge end of the respective transporting unit if the stack is not accelerated before the projections which engage its trailing edge face during transport toward the discharge end of the transporting unit begin to descend to a level below the platform without contacting the trailing edge face of the stack.
One mode of overcoming the just discussed problems is described and claimed in the aforementioned commonly owned copending patent application Ser. No. 417,662 of Bernd Ramcke.
The aforementioned copending application Ser. No. 343,742 further disclosed one mode of converting the transporting units for the treatment of longer or shorter stacks. To this end, the angular position of the first shaft with reference to the second shaft can be changed by loosening or terminating the connection between two clamping discs which are non-rotatably mounted on the first shaft and a pulley or gear which transmits torque to the first shaft. Moreover, the pulleys for the belts can be shifted axially of the respective shafts to thus increase or reduce the spacing between neighboring transporting units. This is necessary when the width of the first series of stacks deviates considerably from the width of the next series of stacks so that the spacing between neighboring units can be reduced if the width of the second series of stacks is a fraction of the width of the preceding stacks or that the spacing between the neighboring units must be increased if the width of the second series of stacks greatly exceeds the width of the previously transported stacks. A drawback of the just discussed proposal to vary the spacing between the neighboring transporting units is that it is difficult to properly align the front pulleys with the rear pulleys subsequent to a shifting of a set of such pulleys axially of the respective shafts. Moreover, the tension of the belts is likely to change during adjustment of their pulleys, and the axial shifting of pulleys often requires the exertion of considerable force, especially after a long period of operation without any adjustment.
Other attempts to improve the operation of conventional apparatus for intermittent transport of stacks of paper sheets or the like include the use of chain conveyors with adjustable pushers or analogous projections. Reference may be had to German Offenlegungsschrift No. 24 56 908. A drawback of such apparatus is that each change of setup takes up a very long interval of time with attendant losses in output, especially if the apparatus forms part of a production line for mass production of pads, books or analogous stationery products. This will be readily appreciated since each of the entraining elements (or at least a substantial number of entraining elements) must be separated from the respective chain, shifted to a different position, and reattached to the chain.